The invention relates to rotary kilns and particularly to the ports for delivering gas and air to the interior of a rotary kiln wherein the port is self-purging.
In the prior art, rotary kilns are known wherein a plurality of ports are provided through the shell of the kiln to admit air and/or fuel into the interior of the kiln.
Examples of such prior art are disclosed in U.S. Pat. Nos. 1,216,667; 2,091,850; 3,182,980; 3,198,235; 3,794,483 and 3,946,949.
In the prior art, kiln fuel and/or air is injected into the kiln through ports while the ports are above the material charge of the bed. Alternately, injection may be accomplished when the ports are beneath the bed of the material charge which consists of fines and larger size particles. Under this condition, the fines and smaller particles enter the ports and associated piping impairing the flow of fluid through the port and eventually causing complete clogging of the port, rendering it useless for under bed fluid injection. It is not unusual to have as many as 300 nozzles in a rotary kiln of 150 foot size. Thus, when a number of ports become useless by reason of being plugged, the efficiency of the kiln is reduced and its operational time span between maintenance periods is reduced, thereby increasing the cost factor. Furthermore, the ports are exposed to extremely high temperatures. While fluid is flowing through a port, the fluid itself has a tendency to cool the port. However, when no fluid flows through the port, the port and associated structure approaches the temperature within the kiln, thereby reducing the effective active life of the port.
It is therefore the general object of the present invention to provide a trap-port construction for a rotary kiln which is self-purging.
Another object of the present invention is to provide a trap-port construction which includes a labyrinth trap design that permits turbulent mixing with resultant particle removal from the port cavities.
Still another object of the present invention is to provide a trap-port construction which minimizes entrapment of fine particulate in the port piping of a rotary kiln.